The charging of electric energy storage systems of motor vehicles by a charging device that is arranged in or on a surface to be traveled over typically requires an exact fine positioning on the order of centimeters in order, for example, to attain an efficiency that is as high as possible during an inductive energy transmission. By way of methods of the kind mentioned in the introduction, autonomously guided vehicle systems are intended to assist drivers or the motor vehicle at least in part when the motor vehicle is aligned with respect to the charging device as a destination, this necessitating the determination of positional data that describes this relative position and is as precise as possible. For this purpose, it has already been proposed to transmit, via the primary coil, an additional low-energy signal, which serves for the fine positioning, or to emit, via an auxiliary antenna at the charging device end, a signal that carries a digital identification code. Likewise, it is known to emit from the vehicle a signal that is received by a plurality of antennas at the charging device end and is analyzed for ascertaining the positional data.
DE 10 2013 110 280 A1 describes a position determination system for a vehicle that can be charged by means of an inductive energy transmission system, wherein additional coils and/or antennas are arranged in a stationary manner, wherein an additional primary-end coil and/or antenna form or forms a primary-end transmitter and at least one additional coil and/or antenna that is arranged at the vehicle form or forms at least one receiver for reception of the signals of at least one primary-end transmitter. For this purpose, at least two receivers and/or at least two transmitters are present, so that the position determination system determines, by means of the transmission signals of the additional coils or antennas, the distance and/or the alignment of the vehicle relative to the primary-end energy transmission device in a stationary arrangement.
DE 10 2013 298 678 A1 discloses a system for alignment of a motor vehicle, comprising a transmitting device that is arranged at a stationary device for emission of electromagnetic waves and a receiving device that is arranged at the vehicle and has at least two receiving units for the detection of electromagnetic waves emitted by the transmitting device. It is hereby provided that the transmitting device comprises at least two transmitting units that are spaced apart, wherein an analysis device is designed for the purpose of calculating an angle between a reference axis of the vehicle and the stationary device on the basis of the distance and orientation of the at least two transmitting units with respect to the at least two receiving units.
When coils are used, methods and systems of this kind are extremely prone to interference because of their small range or on account of overlapping signals when additional transmitting units are used in their vicinity.